And might those ethnic Russians have been there due to a sustained campaign on the part of the Soviets to depopulate the region of ethnic Ukrainians and replace them with ethnic Russians as part of a plan to increase loyalty of the region to the central Soviet authority?

You can justify almost anything if you reach back in history far enough. It’s our responsibility to break the cycle and it’s pretty easy to stop believing the framing of a dictator who only wants to justify his territorial ambitions (and who has made noticeable overtures toward the recreation of the Russian Empire).